234 2 S GROENEWEG and others Triac in health and disease 234:2 R99–R121 Review Triiodothyroacetic acid in health and disease Correspondence Stefan Groeneweg, Robin P Peeters, Theo J Visser and W Edward Visser should be addressed Department of Internal Medicine and Academic Center for Thyroid Diseases, Erasmus University to W E Visser Medical Center, Rotterdam, The Netherlands Email
[email protected] Abstract Thyroid hormone (TH) is crucial for development and metabolism of many tissues. The Key Words physiological relevance and therapeutic potential of TH analogs have gained attention in f thyroid hormone the field for many years. In particular, the relevance and use of 3,3′,5-triiodothyroacetic f resistance to thyroid hormone (RTH) acid (Triac, TA3) has been explored over the last decades. Although TA3 closely resembles f thyroid hormone analog the bioactive hormone T3, differences in transmembrane transport and receptor isoform- f thyroacetic acid specific transcriptional activation potency exist. For these reasons, the application of TA3 derivatives as a treatment for resistance to TH (RTH) syndromes, especially MCT8 deficiency, is topic of f Triac ongoing research. This review is a summary of all currently available literature about the f TA3 formation, metabolism, action and therapeutic applications of TA3. Endocrinology Journal of Endocrinology of (2017) 234, R99–R121 Journal Introduction Thyroid hormone (TH) is crucial for the development and The deiodinases (D1–3) importantly regulate the bio- metabolism of many tissues. Thyroid stimulating hormone availability of T3 in targets cells, while TH is also (TSH) controls the production and secretion of TH by the metabolized by glucuronidation and sulfation, which thyroid gland, which predominantly produces the pro- enhance biliary excretion (Engler & Burger 1984, Burger hormone thyroxine (T4) and to a lesser extent the bioactive 1986, Visser 1996).